Activated carbon is commonly used in many purification systems. Activated carbon derived from carbon precursors is especially useful as an adsorbent because of its continuous uninterrupted structure of random three dimensional graphitic platelets. The platelets have angstrom sized porosity between them, into which contaminants are adsorbed.
In industrial exhaust gases there is typically a mixture of gases that has to be adsorbed from a workstream. An automotive exhaust system, for example contains more than twenty-five different organics. The kinetic molecular diameters of these organics can range from 3-10 angstroms. For such a workstream, one particular carbon structure with a given mean platelet distance may not be the most desirable adsorber. This adsorber would adsorb the large organics much more strongly than the smaller organics, the latter passing through the system unadsorbed.
Furthermore, during desorption it is much easier to remove small organics than large organics. One solution to this problem is to heat the activated carbon adsorber to a higher temperature to remove the large organics. However, this requires a significant energy input.
The present invention relates to a system and method for efficiently removing multiple contaminants from a workstream using more than one activated carbon adsorber with varying pore sixes in the activated carbon, and for efficiently desorbing the contaminants and regenerating the activated carbon for re-use. The adsorption efficiency of the activated carbon is maintained over repeated adsorption-desorption cycles.